Revision Flashcards
Explain why the formation of sea ice is important for global ocean circulation.
When sea ice is formed, the salt in the water is rejected.
This makes the surface waters more dense than the surrounding ice-free waters.
Because the surface waters are dense they sink away from the surface.
As the dense waters sink they are replaced with less dense water, and this process drives a three-dimensional circulation which contributes to the global ocean circulation.
Briefly explain what turbidity is and describe one method of measuring it in a water body.
Which of the following will present greater turbidity values: drinking water or untreated waste water?
Turbidity is a physical parameter used for assessing water quality. It gives a rough indication of the quantity of undissolved matter in water.
(Use one of the following methods for measuring the clarity of water).
The Secchi disk is a flat circular plate (20 – 30 cm diameter) with two quadrants painted black and two painted white.
The disk is lowered into the water until such a depth that it cannot be seen, which provides an indication of the waters turbidity.
The nephelometer is a device that measures the scattering of light at an angle of 90 degrees to the light source.
Light scattering is caused by suspended solids in water and occurs in all directions, however measurements at this angle are able to see smaller particles.
Briefly state two relative advantages for each of the following methods of measuring a minor atmospheric constituent in the troposphere and stratosphere:
(a) Using a balloon.
(b) Using a polar-orbiting satellite.
(a) Relative advantages of a balloon measurement (any two from):
- Cheap and/or quick to build, launch and operate.
- Can measure more easily under cloud cover or close to the surface.
- The atmosphere can be sampled directly, in contrast to a remote indirect measurement.
- Measurements can be made as the balloon ascends, giving a more detailed vertical profile.
- Not necessarily restricted to a gas that has distinct absorption features at wavelengths in atmospheric spectral windows.
(b) Advantages to a polar-orbiting satellite measurement (any two from):
- Global coverage with a single instrument.
- May operate for periods of several years, giving better coverage in time.
- Provide access to regions where it is difficult to launce balloons, for either geographical or political reasons.
- Can potentially measure over a larger altitude range.
Chlorofluorocarbons CFCs, are anthropogenic compounds, which add to the normal background level of stratospheric chlorine and have been linked to ozone depletion in this region.
(a) Chloromethane CH3Cl, is a natural source gas for chlorine atoms in the stratosphere.
Give one origin of this gas at the Earth’s surface.
(b) One CFC linked to stratospheric ozone depletion is CFC-113 which has an atmospheric lifetime T of 90 years.
To the nearest whole year, determine how long it will take for the atmospheric concentration of CFC-113 to fall to quarter of the level reached when all emissions cease.
(The lifetime of an atmospheric gas is related to the half like, t1/2 as t1/2 = 0.693 T.)
Natural sources at the Earth’s surface of CH3Cl are (any one of the following origins):
Formed by natural processes from the oceans. Burning of biomass. Volcanic activity. It will take two half-lives to reduce to a quarter of the atmospheric concentration, so one half-life is: t_(1/2)= 0.693 X 90=62 So two half-lives are: 62 X 2=124
It will take 124 years for the concentration of CFC-113 to fall to quarter of the level reached when all emissions cease.
Briefly describe two major properties of soil organic matter that can enhance plant growth.
Any two of the following properties which can all enhance plant growth:
- Nutrient supply: the breakdown of soil organic matter releases nitrogen, phosphorus and sulfur (among other nutrients) that can be used by plants.
- Ion adsorption and desorption: through its high cation exchange capacity, organic matter can hold and release large amounts of nutrient cations in a form readily available to plants.
- Structure: humus binds soil particles together, stabilising the structure and allowing water and air to pass through to lower layers, as well as enabling easier root penetration and seedling emergence.
- Water holding capacity: organic matter has a high capacity to retain water, and the structure of soil that is rich in organic matter allows for easier water infiltration and reduced runoff.
- Colour: the dark colours characteristic of humus-rich soils absorb more sunlight at the surface than those of a lighter colour and, therefore give rise to warmer soils.
Briefly describe the mechanism by which beach sediment is transported along a coastline.
Most waves strike the shore at an oblique angle. When oblique-angled waves hit a shoreline, they are reflected and generate a longshore current which flows parallel to the shore.
Because waves strike the beach at an angle, the swash of the wave travels obliquely up the beach, but the backwash flows straight down the beach.
The result is beach drift, a zigzag movement of sand and pebbles along the shore.
Beach sediment transport along the coastline results from the longshore current and beach drift. This transport is called longshore drift.
Briefly describe the main factors determining the physical structure of habitats.
Physical structure of habitats is generally defined in terms of the dominant vegetation, such as trees or grasses.
Vegetation influences physical factors, for example habitat height, exposure, light regime and humidity.
Vegetation structure is affected by both abiotic growing conditions (climate, geology, soil), biotic factors (e.g. activity of organisms within the habitat: grazing, trampling, competition for light), and human activity.
The physical structure of aquatic environments is linked to the water depth, speed and turbidity.
Some habitats – such as caves, cliffs, glaciers, rock exposures, urban developments – do not have vegetation as the dominant structural factor.
(a) Define species richness and species diversity.
(b) Two ecological communities may have the same number of species but score differently for measures of diversity.
Explain why this is the case.
(a) Species richness is the number of species in a site.
Species diversity is the number of species weighted by their relative abundance
(b) If one community is dominated by one or a small number of species and the other has a more even distribution of species the second community should be expected to score higher for diversity.
Give one example of how sulfur may move naturally from the terrestrial crust into the atmosphere or oceans.
Explain how anthropogenic activities are increasing the flux of sulfur from the crust.
Sulfur-containing rocks (including shales and evaporites) eventually move into the oceans vai natural weathering and erosion.
Humans are increasing the flux of sulfur from the crust by mining and extraction of fossil fuels that contain sulfur.
Combustion of fossil fuels results in emission of sulfur to the atmosphere, much of which will be redeposited on land, or into the oceans through riverine flow or by directly being deposited on the oceans.
Describe the causes and symptoms of eutrophication in aquatic environments.
Eutrophication is caused by an excess of nutrients in the water.
It usually causes explosive growth of algae or bacteria.
The volume of material can block sunlight, preventing autotrophs from photosynthesising, so oxygen levels in the water decline.
This can lead to increased mortality of animal life.
Exhaust emissions from the internal combustion engine of motor vehicles can give rise to several primary pollutants in addition to H2O and CO2.
(a) Name one of these primary pollutants and describe how, and under what conditions, it is formed.
(b) The action of sunlight and the mixing of primary exhaust emissions gives rise to various secondary pollutants, such as ozone.
What is the term used to describe this type of pollution, which often occurs in urban areas?
(a) There are a total of four primary pollutants emitted from a vehicle (only one is required)
- Carbon monoxide (CO) and unburnt hydrocarbons (HCs), which are produced by incomplete combustion of fuel during traffic idling (and deceleration) when insufficient air is taken in for complete combustion to occur.
- Nitric oxide (NO), which is generated by the fixation of nitrogen from the air at the high temperatures in the engine.
- Particulate matter (PM), which again comes from the incomplete combustion of the fuel in the engine and is dependent on the type of fuel and engine conditions.
(b) This type of pollution is referred to as photochemical smog
A sample of the mineral Almandite has the formula:
Fe3Al2Si3O12
What is the formal charge on iron (Fe) in this mineral, i.e. is the iron Fe(II) or Fe(III)?
Explain how you reached your answer, showing your calculations.
All the components of this mineral have fixed formal charges except Fe.
The other components are Al3+; Si4+; O2-
The sum of the positive charges must equal the sum of the negative charges.
Sum of positive charges
=[3 x (Fe)]+[2 x (Al)]+[3 x (Si)
=[3 x (Fe)]+[2 x 3]+[3 x 4]
=[3 x (Fe)]+6+12
=[3 x (Fe)+18
Sum of negative charge
=12 x (O)
=12 x 2
=24
Therefore, charge on Fe
= ((24-18))/([3 x (Fe)])
= 6/3=2
The iron is in the Fe(II) form
Seed size varies greatly between different species of plant.
Describe any ecological trade-offs that exist with the respect to this attribute and the colonization of new habitats.
Small seeds can be efficiently dispersed, but have poor survival in hostile environments.
Large seeds have a better chance of survival, but may not be able to reach the new environment.
Describe the time-scales on which the carbon cycle operates.
The carbon cycle involves a hierarchy of subcycles that operate on different timescales, stretching from years to millions of years.
The terrestrial carbon cycle is the shortest term subcycle, with residence times of tens of years.
The marine carbon cycle is the intermediate-term subcycle, with residence times of thousands of years.
The geological carbon cycle is the long-term subcycle, with residence times of millions f years.
The sea surface in the centre of a North Atlantic gyre, which is rotating in a clockwise direction, is raised by about 1 meter.
Briefly describe the reason for this.
You should include a sketch as part of your answer.
The sea surface is raised (in the Northern Hemisphere) because Ekman pumping results in water flow at 90° to the right of the current direction, i.e. towards the centre of the gyre.
Water piles up in the centre of the gyre, raising the sea surface, see sketch below
Describe and account for differences in the annual variation in runoff from a river in southwest England and a glacier fed stream in western Greenland.
In southwest England, runoff is likely to be highest in the winter months when rainfall is relatively high and evapotranspiration is at its lowest rate.
In western Greenland, the glacier is frozen during the winter and does not feed into the river, so runoff is low to zero at this time. However, in the summer the glacier melts so runoff will be highest at this time.
Briefly Describe the difference between porosity and permeability in rocks, and use these concepts to explain why chalk is a good aquifer.
A rock is permeable when water can flow easily through it, whereas the percentage of a rock that is comprised of space is its porosity.
Chalk has both high permeability and high porosity, and thus is a good aquifer.
The high permeability means that water can flow through it easily and the high porosity means that it can retain a lot of water.
Outline two ground surface features that act to reduce rainwater infiltration
(any two including the mechanism)
Dense vegetation, through the interception of rainfall
Steep slopes, as water runs off rapidly reducing time for infiltration to occur
Concrete / Roofs / Covered surfaces all of which prevent water passing through
Saturated ground can become frozen and form permafrost in polar regions or at high altitudes.
(i) Why is there very little permafrost in the Southern Hemisphere?
(ii) Why is widespread flooding common in permafrost regions?
(iii) Why is the progressive thawing of permafrost of concern?
Most of the land where permafrost could form in the Southern Hemisphere is already covered with glacial ice.
(ii)
In winter rivers are frozen and their flow is minimal. As the thaw occurs, ice dams are common features and the rivers become blocked and flood their banks. In addition, the permafrost is relatively impermeable.
(iii)
Progressive thawing of permafrost is a concern because
Many buildings are constructed on permafrost. As the permafrost retreats their foundations may become unstable and cause buildings (and other structures and trees) to collapse. It can release methane, which is a greenhouse gas so will likely cause increased atmospheric warming.
A researcher is interested in assessing how flow rate in a small river changes seasonally and over several years. Describe the equipment they could use and the data they might collect using this method. Explain some of the disadvantages of using your suggested method.
Since the researcher is interested in looking at change over several years as well as with the seasons, they could look to build a v-notch weir with a stilling well
Providing the weir can be built on an impermeable bedrock, so that there is no groundwater flow, or throughflow via the soil, out of the catchment.
If the weir is not on an impermeable bed, an allowance must be made for these other pathways.
This equipment is suitable for assessing flow rate over long periods of time and does not require frequent visits to the site. The stilling well would contain a logger or chart recorder which would continuously record the height of the water: the more water flowing down the stream the higher the water level recorded by the logger or chart recorder.
Flow rate can be calculated directly from the water height.
The disadvantages of this method are that it is expensive to install and involves some disturbance of the system. It may therefore not be suitable for all sites or purposes.
Briefly describe the processes that allow the climate system to maintain an equilibrium temperature on average, despite the difference between the two curves in Figure 2.
Polewards heat transfer in the atmosphere is required to maintain an equilibrium temperature.
This is largely accomplished by the Hadley circulation at low latitudes, and by frontal cyclones at mid latitudes, which develop on fronts separating warm and cold air masses and transport heat and moisture poleward and upwards.
Heat is transported by the movement of warm air polewards, or in the form of latent heat transport by evaporation at lower latitudes
Describe how incoming and outgoing radiation vary with latitude for typical July conditions compared to the annually averaged conditions illustrated in Figure 2.
Explain how this change in radiation will change the Hadley cells, compared to their annual average form.
In July, the incoming radiation is shifted towards the Northern Hemisphere as a result of the seasonal variation of insolation, peaking at around 23° N.
It drops to zero south of around 67° S (the Antarctic Circle) because of the Earths tilt.
The outgoing radiation curve is less strongly affected, as this depends fundamentally on the absolute temperature of the atmosphere, but compared to the annual average it would be slightly lower in the Southern Hemisphere and slightly higher in the Northern Hemisphere.
In the annual average, the Hadley cells are symmetrical about the equator, with rising branches at the Equator, the point of maximum net heating.
In July, the rising branches will move north with the point of maximum incoming radiation (and so maximum net heating), resulting in rising motion north of the Equator and a larger, weaker cell crossing the Equator into the Southern Hemisphere.
Stratospheric ozone is created and destroyed in the cycling of reactions known as the Chapman mechanism
Figure 3 A reaction cycle showing the creation and destruction of Stratospheric ozone
(i) The first reaction in the cycle involves the photolysis of an oxygen molecule, O2 Write out this reaction and define what is meant by ‘photolysis’
(ii) From Figure 3, Write out the other three reactions in the cycle.
Briefly indicate the processes involved in each reaction with respect to the production and destruction of ozone in the stratosphere.
(iii) Stratospheric ozone is an important filter of UVB radiation.
If ozone is destroyed in the stratosphere what effect will this have on the absorption of UVB radiation and potential consequences at the Earth’s surface?
(i) The reaction at the top of the cycle is
O2 + hv → O + O (R1)
In Reaction 1, photolysis is the fragmentation of a molecule of O2 initiated by the absorption of ultraviolet radiation (hv) at a wavelength of about 240 nm, generating highly reactive free atoms and/or radicals of O.
(ii) From the reaction cycle:
Free O atoms generated from Reaction 1 combine with O2 molecules to form ozone
O2 + O → O3 (R2)
Ozone adsorbs ultraviolet radiation (hv) itself, which leads to photolysis in:
O3 + hv → O2 + O (R3)
Ozone encounters a free O atom and is converted back into O2
O3 + O → 2O2 (R4)
Hence, ozone is being created and destroyed in the cycle by Reactions 2 and 3, and finally removed from the cycle by Reaction 4.
(iii) Ozone destruction would increase UVB radiation reaching the Earth’s surface and potentially cause an increase in its harmful effects, such as damaging DNA, proteins, lipids and membranes in plants and animals at the Earth’s surface as well as sunburn, eye damage and skin cancer in humans.
Explain any five functions of soil on the Earth’s land surface.
(A) Any five of the following functions of soil:
• Water storage for vegetation and life forms:
Soils retain water which is available to a variety of organisms in different ways.
Soils differ in their capacity to store water and organisms which use soil water vary in their ability to extract water stored in soil.
• Habitat:
Soils are home for many organisms which live exclusively or predominantly in them.
• Nutrient storage and retention:
Macro-nutrients such as Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulfur, calcium and magnesium as well as a range of micro-nutrients including iron, manganese, boron, zinc, copper, chlorine, molybdenum, cobalt and nickel are stored in soils
Different soils have different capacities for nutrient storage and retention.
• Nutrient recycling:
Carbon, oxygen, nitrogen and other nutrients are recycled through the action of plants, fungi and microbes in the soil.
• Structural support to plants:
Soil gives plants a medium to grow into.
Different soils are able to support plants differently.
• Filtration and purification of toxins:
Toxins may be broken down or filtered out by biotic or abiotic processes in soil.
Briefly outline the role that naturally acidic rain plays in rock weathering.
Rainwater dissolves carbon dioxide from the air and so is naturally slightly acidic.
This has a particular effect on the chemical weathering of carbonite rocks and leads, for example to underground cave systems in limestone areas.
This weak acid is also the initiator of the chemical reaction between silicate rocks and water, known as hydrolysis.
Feldspar exposed to an acidic aqueous solution of carbon dioxide reacts, releasing metal ions and dissolved silica into solution and leaving behind a solid clay mineral, kaolinite.
{12 marks} Discuss the causes of soil acidification that occur:
(i) Naturally with time, and
(ii) As a consequence of human action.
Soils may acidify naturally as plants take up positively charged nutrients which are exchanged for acidifying hydrogen ions.
However, basic cations are normally returned to the soil, which should counteract this acidification, as broad-leaved trees shed their leaves and, eventually, die.
This is why the development of coniferous forests over time leads to greater soil acidification. (unless the underlying geology means that the soil is well buffered against this.)
(ii)
Acid deposition may occur as a consequence of atmospheric pollution, with atmospheric sulfur being the main acidifying agent. (Nitrogen deposition is also important for acidification.)
Afforestation by humans may also lead to soil acidification, as this often involves extensive coniferous plantations.
Also, as trees are harvested, basic cations are exported from the ecosystem resulting in acidification.
Explain with reference to Figure 4, the distinction between population extinctions due to chance (random) variations in population size and extinctions due to a consistent reduction in the size of the population.
Name one cause of chance variation and one cause of consistent reduction
The figure contrasts extinction due to chance (random) events with no long-term change in average size (Figure 4a) with extinction due to consistent reduction in population size with little variation around the mean (Figure 4b).
Extinction may also be due to a combination of the two processes, as shown in Figure 4c.
Chance events may be due to annual climate variation causing direct mortality or affecting food supply, while consistent reduction may be due to continuous habitat loss, possibly through direct anthropogenic activity, or long-term trends in climate (rising sea levels, increased mean temperature).
Explain how Population Viability Analysis can be used to inform the conservation of threatened species.
Population Viability Analysis (PVA) is the application of population dynamics theory to the conservation of rare species.
It aims to help estimate the probability that a population or a species will go extinct within a certain timeframe.
This allows a risk of extinction to be estimated.
Population Viability Analysis has been used to estimate the minimum viable population required for a species to persist.
How does the International Union for the Conservation of Nature (IUCN) Red List use information on population size, population change and extinction risk to categorise threatened species?
The IUCN Red List categories threatened species as follows: Extinct (+ extinct in the wild) Critically Endangered Endangered Vulnerable
Based on different factors
Species with small populations are given higher threatened status than those with large populations.
Species which are experiencing rapid population declines are given higher threatened status that those with stable populations.
Species where PVA has identified a high risk of extinction are given higher threatened status than those with low risk.
A group of conservation biologists were concerned about the effect of woodland management on population of a rare butterfly in Britain.
They wanted to compare population density of the butterfly in ten woodlands which were being managed with coppicing with ten woodlands which were not coppiced.
(i) Explain what coppicing is and how it affects woodlands.
(ii) Describe a study that conservation biologists could carry out to answer their question.
Write down a suitable study hypothesis and null hypothesis.
State an appropriate statistical test foe the comparison between woodlands and explain why you have chosen that test.
Coppicing is the cutting of trees at their base periodically to encourage new growth.
It opens up areas of woodland, and forms a mosaic of conditions allowing light from the canopy to reach the forest floor and creating structural diversity which provides increased niches for a range of species.
It can benefit a range of woodland species
(ii)
The conservation biologists could carry out visual surveys of butterflies using a walk and count method in each woodland.
They would need to ensure that they walked the same survey line/ transect length in each woodland to make it a fair comparison between sites.
They should do several transects in each woodland to account for habitat variation in each woodland.
They should do their surveys in similar weather conditions and at similar times of day to make them comparable.
A suitable study hypothesis would be:
Coppicing has a significant effect on butterfly population density
A suitable null hypothesis would be:
There is no significant difference between butterfly population density in coppiced and un-coppiced woodlands
Because the study is looking at differences between two samples the Mann-Whitney U-test would be appropriate for a statistical analysis,
Describe how population size can be assessed in insects and elephants
Assessment of population size generally requires sampling of the population rather than counting all the individuals in a population.
Sampling involves counting part of the population or using indirect estimates of numbers of individuals and then scaling up to the whole population.
Examples relevant to insects include walk-and-count with mark-release-recapture.
Elephant numbers can be assessed by sampling density of dung.
Explain using appropriate examples, how information on variation in population size from year to year could be included in a plan to conserve a species of woodland butterfly.
Variation in population size is an important factor to consider when assessing the likelihood of population extinction (see answer to part ‘a’ of this question).
This variation can be quantified as standard deviation around the mean.
A population with higher variation around the mean and a lower mean population size is likely to be more vulnerable, i.e., more likely to go extinct.
This information can be included in population viability analysis and combined with other information, such as geographic range in Red List criteria.
A plan to conserve woodland butterfly species should respond to information on population variation, e.g., high variation may be due to seasonal changes in host plant availability for breeding butterflies.
Management, such as thinning the canopy to maintain a suitable light environment for the host plant, could help reduce the variation in population size.
Briefly explain how an ecosystem services assessment might benefit the conservation of African elephants.
Ecosystem services provide a way of valuing different components and functions of an ecosystem.
African elephants, as large and iconic herbivores, may provide a cultural services (both to local people and more widely to visitors, with possible benefits of ecotourism income).
Maintenance of large grassland or savannah ecosystems may also contribute to other ecosystem services (provisioning, regulating or supporting).
Describe the different ways in which dinitrogen gas (N2) may be transferred from the atmosphere to terrestrial nitrogen reservoirs.
Pay particular attention to the different fluxes and processes in your answer.
Nitrogen in the form of dinitrogen (N2) is chemically stable, and so is not useful to terrestrial ecosystems in this form. The nitrogen must therefore be “fixed” into a form that is biologically available. N2 can be fixed naturally and artificially, as explained below.
A small natural component of the total amount of bioavailable nitrogen is fixed by lightening, which converts N2 to NO. The NO then reacts to form NO2 and subsequently HNO2 and HNO3, which are deposited on land in rain water.
However, overwhelmingly, the majority of nitrogen fixed directly from the atmosphere is vai nitrogen-fixing organisms.
Such as certain species of free living cyanobacteria, and bacteria that exist in a symbiotic relationship with plants such Rhizobium bacteria which lives in the root nodules of legumes.
Dinitrogen may also be fixed through an industrial process known as the Haber-Bosch process. Here N2 is reacted with H2 under high temperatures and pressure in the presence of a catalyst to form ammonia (NH3). This ammonia is then used in the production of fertiliser, which is available for plants so can enter the terrestrial reservoir.
Briefly explain how nitrogen in terrestrial reservoirs may be transferred to the atmosphere.
Ammonia (NH4) can be volatilised from soil.
Nitrate (NO2) can be denitrified in oxygen-poor soils to form N2 N2O or NO
(i) What is the main anthropogenic source of atmospheric nitrogen?
Explain how anthropogenic nitrogen in the atmosphere affects the amount of biologically active nitrogen in terrestrial ecosystems.
(ii) Describe how an increased amount of biologically active nitrogen affects the composition of a terrestrial plant community.
(i)
The main anthropogenic source of nitrogen within the atmosphere is produced by the combustion of fossil fuels, for example from vehicles and powerplants.
The burning of fossil fuels releases NO into the atmosphere, which will react further with O2 to form NO2.
Both NO and NO2 are highly soluble in rain/cloud water to form HNO2 and HNO3 is deposited in rain and dissociates to release biologically active NO2- and NO3-
(ii)
An increased amount of biologically active nitrogen can change the plant species within a terrestrial community, which will impact the community composition.
The biomass of species that can respond to the elevated nitrogen by increasing growth or productivity will increase; whereas, in contrast plant species that are unable to adapt to the high concentration of nitrogen by increasing their growth will be eliminated through competition. Therefore, overall it is likely that the species richness will decline.
Figure 5 is a Hjulstrőm diagram. Using this diagram as a guide, describe the erosion process and the processes of detachment, entrainment and deposition
The process of erosion can be seen as a sequence of three events: detachment, entrainment, and transport.
Erosion begins with detachment, where a piece of rock is released from the rock around it, to become an unattached rock fragment.
Physical weathering leads to detachment by purely mechanical means which can occur in many different ways.
Chemical weathering breaks down minerals formed at higher temperatures and pressures and transforms them into new minerals that are more stable at the Earth’s surface.
Biological weathering can facilitate detachment by providing cracks and fissures that may be exploited by physical and chemical weathering.
Entrainment is the process which lifts particles off the bed or ground and sets them in motion.
Entrainment is resisted by friction between the particle and its neighbours and the force of gravity.
If the drag created by the fluid is sufficient to overcome the horizontal resistance of friction and vertical resistance gravity, the particle will begin to move.
The critical speed at which entrainment occurs is related to grain size.
The largest (heavy) and smallest (cohesive) particles are entrained at higher speeds.
Transport can occur in four different ways: solution, suspension, saltation and traction.
Transport will continue until there is a reduction in the speed of the medium or an increase in the resistance of the particles (i.e. flocculation).
If either of these occurs, the ability of the medium to transport will be reduced and deposition is the result.
Explain how rates of glacial erosion are inferred using glacial meltwater and list the variables that can affect the reliability of this technique.
Rates of erosion for glaciers are frequently inferred by the sediment yield of a glacier, i.e. the mass of sediment per unit area by melt water.
This is relatively easy to measure and should reflect the rate at which sediment is produced by erosion beneath the glacier.
It is not yet possible to define a constant relationship between glacier formation and sediment yield because of several variables:
- Variations in glacier mass balance and flow rate.
- Nature of the bed rock.
- Stability of the channels.
- The relaxation time of the previous glaciations, i.e. the abundance of transportable sediment exposed during glacial retreat.
- Variations in meltwater discharge.
Using your knowledge both of energy flow through ecosystems and of habitat fragmentation, explain why populations of large carnivores are now particularly susceptible to extinction.
Your answer should address:
(a) {7 marks} Food chains, including energy transfer and efficiency;
(b) {7 marks} range and energy requirements;
(c) {6 marks} habitat requirements and habitat changes.
Large carnivores will tend to be at or near the top of the food chain. Probably secondary or tertiary consumers.
There are therefore three or four steps in the food chain between the original energy source, sunlight, and these large consumers.
The potential for energy to enter an ecosystem is determined by the amount of solar radiation it receives, which in turn is determined by its area and position on the globe.
The transfer of energy from one trophic level to the next is inefficient.
Typically, only 0.1% of solar radiation becomes stored in the tissues of primary producers.
Less than 1% of this would be expected to become incorporated into the tissue of a primary consumer in many ecosystems. And each additional step of the food chain would result in a further 90% loss of available energy.
Therefore, tertiary consumers would have only 0.001 x 0.01 x 0.1 = 1 x 10-6 of the energy entering the system potentially available to them as prey, whilst in contrast a primary consumer would have 10-3 of this amount of potentially available to them as food, a difference of 1000. {NB these values are dimensionless in the model answer!!}
One could therefore estimate that for a tertiary consumer to sustain a population as large as that of a primary consumer of similar body size, it would require a land area 1000 times larger. Even if the large carnivore were a secondary consumer (e.g. a lion), this figure would still be 100.
The result is that large carnivores need a very large range to support their energy requirements.
Examples of large carnivores: bears, wolves, tigers, eagles and sharks.
These are highly mobile animals moving over large distances to locate and kill prey.
Habitat fragmentation has two effects on the range of large carnivores.
First, it reduces the total area of habitat and therefore reduces the amount of energy entering the ecosystem (for example the fragmentation of woodland in Britain has reduced its total area by more than 95%).
Second, it may introduce barriers to movement of these animals within their range. Dissection of forest with tracts of open grassland may confine predators to small blocks of woodland because they are unwilling to cross unfamiliar. {NB the model answer just stops there! I would add territory or ground to finish the sentence}
In summary, large carnivores require large tracts of suitable habitat to sustain them because of the inefficiency of energy transfer up the food chain.
Fragmentation of the habitat may confine populations to areas too small to sustain them in the long term. Putting them at risk of extinction.
In addition to its effect on area, habitat fragmentation causes other changes to the environment which may place large carnivores at greater risk of extinction.
Disturbance from human activity (logging, ranching, fishing, etc.) may impact on the behaviour of both the carnivores themselves and that of their prey, upsetting the predator / prey balance.
Opening up a habitat such as a forest during its fragmentation provides routes such as logging tracks along which {human} hunters can travel. Large carnivores are often targets for such hunters and so there could be a top-down control on their population size.
(ii) {2 marks} Some researchers have argued that the changes in the pH of the lake are not due to acid rain but to other processes.
Briefly outline two processes other than acid rain that are thought to lead to acidification of lake waters.
(iii) {2 marks} Name the gas that is primarily responsible for causing acid rain.
What is the principal source of this gas?
(iv) {2 marks} In the introduction to part (b) of the question, it is stated that the fish population of Big Moose Lake has declined.
Why does acidification of lake waters lead to a decline in fish populations?
(v) {2 marks} Indicate the two principal approaches taken to manage the problem of lake acidification.
(ii) Natural acidification (e.g. respiration by plant roots)
Change in land use (e.g. conifer afforestation / heathland regeneration / decline in upland agriculture)
(iii) Sulfur dioxide
Burning fossil fuels
(iv) Acidification leads to an increase in dissolved aluminium (Al3+) in lake waters and this is thought to lead to fish kills.
(v) Liming of lake waters to counteract acidity
Reduction in sulfur emissions
How can water content of soil be determined?
By drying the soil in an oven
Soil is weighed Then put in an oven at 105 degrees where it is dried for 24 hours The soil is then weighed after The mass loss represent water 1L = 1kg
What are held in the pores of soil?
Water and air
How big is a micropore?
<0.08mm
How big is a macro pore?
> 0.08mm
What is porosity?
The ratio of the volume of void spaces in a rock or sediment to its total volume
What is secondary porosity?
Porosity that has been caused by fractures or weathering in a rock or sediment after it has been formed
What is air filled porosity?
The proportion of a soils volume that is occupied by air
What type of soil do macropores generally dominate?
Sandy soils
What type of soil does micropores generally dominate?
Fine textured soils eg clay silt
What can macropores be created by?
Crack opening by clay that has been wet and then dried
Soil freezing and thawing
Living organisms roots, worms, termites
What is considered unavailable water in terms of soil moisture?
There is still water in the soil below the PWP, but it cannot be extracted by plants and is therefore called unavailable water.
Are micropores usually filled?
Yes they are most of the time filled with water
What type of soils have greater water holding capacity and why?
Fine textured soils dominated but clay or silt have better water holding capacity because they are made of micropores which are mostly filled with water all the time and are poorly drained so are prone to flooding
Do sandy soils have good water holding capacity?
No they are made of macropores so the rapid movement of water and air occurs
Larger pores may be filled with roots
What does the rate of percolation depend on?
The rate of percolation is highly dependent on soil structure and texture. The rate of water movement is greatest in sandy soils or very well-structured soils.
How can you determine the porosity of soil?
Take an undisturbed core of soil Saturate the soil with water Weigh it Then completely dry out the soil Weigh it again
Porosity % = saturated mass - dry mass(coverted to volume)/volume of core
A soil is sampled, using a soil core of volume 100 cm3, and the difference between saturated mass and dry mass is determined to be 50 g.
Given that the density of water is 1 g cm−3 at room temperature, calculate the porosity of the soil.
Because 50 g of water occupies 50 cm3 in total:
Porosity = 50 cm3/100 cm3 x 100
Thus the porosity of this soil is 50 cm3 of pores in 100 cm3 of undisturbed soil, or 50%.
In addition to total pore space, what is it important to know for estimating important properties of soils, such as ease of drainage?
It is important to know the proportions of different sizes of pore, particularly the relative proportions of macropores to micropores, and how the pores are connected together.
Does clay give plants good availability to water?
despite its high porosity, much of the water in a clay-textured soil (pores < 0.0002 mm or < 0.2 µm in size) may be held with such strength that it is not available to plants. Such a soil may have a high water content but poor water availability.
What type of soil can plants get better water availability?
On the other hand, free-draining sandy soils, with large pores, may contain little water in those pores. Most of them may be filled with air. Usually, it is the intermediate-sized pores (0.2–80 µm) which store water that is available for plants to use
What is permeability?
The permeability of a soil is the ease with which water passes through the soil.
How is permeability related to porosity?
Permeability is related to porosity, pore size distribution and how well the pores are interconnected. Pores must be large enough for water flow to occur; so clay soils have high porosity but low permeability.
Describe the porosity and permeability of clay
clay soils have high porosity but low permeability.
What is field capacity?
When the last drop of water has fallen from the pot, the drainable water has drained away and the soil is said to be at field capacity (FC). In this condition, the soil is holding as much water as it can against the force of gravity
What is available water in terms of soil moisture?
The amount of water held between field capacity and permanent wilting point is called the available water.
What is permanent wilting point?
When the plant will be unable to extract sufficient moisture to survive.
At this point, the soil is said to be at its permanent wilting point (PWP)
What is considered unavailable water in terms of soil moisture?
There is still water in the soil below the PWP, but it cannot be extracted by plants and is therefore called unavailable water.
How does soil water content at field capacity differe from different textures of soil
The soil water content at field capacity differs greatly for different textures of soil. In general, the finer the texture of the soil, the more water it can hold at field capacity. Soils with a high clay content can hold several times more water at field capacity than very sandy soils
What is infiltration?
Infiltration is the process whereby water from rainfall, irrigation or snowmelt enters the soil pores and becomes soil water.
What is percolation?
Once it has infiltrated, water moves through the soil by percolation. If the soil is wet, or the rainfall intensity is high, the water will move rapidly through the larger pores
What is the water cycle and what is it driven by?
• The water cycle involves the movement of water, in all its forms, over, on and through the soil and rocks near the surface of the Earth and in the atmosphere. This cycle is driven by the Sun’s energy and the Earth’s gravity.
What are the three mechanisms for soil water movement?
There are three mechanisms of soil water movement:
saturated flow
unsaturated flow
as water vapour.
What does the movement of water into and through a soil have implications on?
The movement of water into and through a soil has implications for soil formation, plant growth, surface runoff and erosion. It also has implications for the transport of nutrients and pollutants.
How will water percolate through soil if it is dry and the rain intensity is low?
If the soil is dry, or the rainfall intensity is low, water will move more slowly than in wetter soils, and it will move through the finest pores. These differences are important because water moving more slowly through finer pores has more time to react chemically and physically with organic matter, clay particles, soil minerals and the soil biota.
What are the major components of soil solution?
The major components of the soil solution include:
ions derived from atmospheric deposition
carbon dioxide from root respiration
dissolved nutrient ions from the decomposition of organic matter
dissolved inorganic ions from weathering.
What ions from atmospheric deposition (rain and snow) are found in soil solution?
Rain and snow typically contain:
basic cations (Ca2+, Mg2+, K+, Na+) from dust, sea spray and volcanoes
anions, for example Cl− from sea spray, NO3− and SO42− from car exhaust gases and power stations
ammonium (NH4+) from the agricultural emission of ammonia (NH3)
CO2 from the atmosphere and H+ from acids.
How do ions from atmospheric deposition affect the soil and plants?
Dust particles which have been filtered out by leaves (conifers are particularly effective at this), atmospheric chemicals adsorbed on leaves or bark, or aerosols absorbed into leaves can all be washed to the soil surface in rain or snowfall. This precipitation, with its dilute chemicals, percolates through the soil.
The cations are often vital nutrients for vegetation. They also play an important role in maintaining a high soil pH.
The anions, particularly nitrate, are also plant nutrients. Sulfate is a plant nutrient but is usually not required in large amounts. The excess either washes through the soil solution or is adsorbed by hydrous oxides or organic matter. Chloride is barely used by most plants and washes away through the soil.
Explain how root respiration create CO2?
Levels of dissolved CO2 in soil solution can easily exceed atmospheric CO2 concentrations by a factor of 10 or more. This is because of root and microbial respiration, especially in warm, wet climates where respiration is high.
By creating high concentrations of CO2 in the soil, living organisms strongly influence the geochemical process of rock weathering.
What dissolved nutrient ions from the decomposition of organic matter are found in soil?
Organic material is rich in carbon and nitrogen. It also contains phosphorus and other elements. These nutrients are released into the soil solution during decomposition, making them available for use by plants and microbes. Dissolved C, N and P compounds are often rapidly recycled back into living matter.
What dissolved inorganic ions in soil come from weathering?
The basic cations Ca2+, Mg2+, K+ and Na+ are made available to the soil solution through cation exchange with clays and organic matter. But their primary source is usually rock weathering.
Phosphorus is also supplied to the soil from the weathering of rocks, in particular those containing the mineral apatite.
The concentration of dissolved silica in the soil solution is also regulated by the rates of chemical weathering of the silicate matrices in clays, and the minerals in silicate rocks.
What percentage of soil is air and what pore does air usually occupy?
It may not be immediately obvious that soil contains air. In fact, most soils contain about 25% air by volume. Whereas most soil water is held in the smallest pores, soil air is usually held in larger pores.
What type of soil have more pore space?
Sandy soils generally have a higher dry bulk density than clayey soils. In other words, sandy soils have less pore space than clayey soils. At first, this may seem difficult to believe, because sandy soils usually appear more porous than clayey soils.
However, sandy soils have only a relatively few very large pores and almost no small pores, whereas clayey soils have many extremely small pores. In other words, the total pore space is greater in clayey soils.
How is the oxygen that plants receive controlled mainly by?
The amount of oxygen is controlled mainly by macropore space, soil water content and oxygen consumption by soil biota.
What is the hydraulic head determined by?
The speed of water movement down a slope through saturated soil between two points in a catchment is determined by the hydraulic head, the hydraulic conductivity of the soil and the distance between the two points (Darcy’s law).
What are the chemical constituents of soil air?
Soil air is held in larger pores. The chemical constituents of soil air include oxygen, carbon dioxide, methane and nitrous oxide.
What is dry bulk density?
Dry bulk density is the mass of a specific volume of dry soil and, therefore, includes pore space as well as solids.
What is the water cycle and what is it driven by?
• The water cycle involves the movement of water, in all its forms, over, on and through the soil and rocks near the surface of the Earth and in the atmosphere. This cycle is driven by the Sun’s energy and the Earth’s gravity.
What does the depth of saline water under a land at the coast depend on?
There is usually saline groundwater under the land at a coast, with a wedge of denser saline groundwater under the fresh groundwater. The depth to the saline groundwater depends on the height of the water table above sea level and the densities of the fresh and saline water.
What is residence time of water?
• Residence time is also a measure of the rate at which water in different parts of the cycle is renewed: it is fastest in the atmosphere (about 11 days) and rivers (a few weeks).
How to calculate residence time for water?
• The residence time for water in a reservoir is the average length of time that water remains in that reservoir. It is calculated by dividing the mass in a particular reservoir by the rate of transfer to or from the reservoir.
What is interception?
Interception is the process by which precipitation is prevented from reaching the ground by vegetation.
Where is precipitation the greatest?
• Precipitation has a very uneven global distribution, but is greatest near the Equator. On a smaller scale, precipitation is greatest over mountainous areas on land.
How is water returned to the atmosphere?
Water is returned to the atmosphere by evaporation and transpiration
What is transpiration?
Transpiration is the process by which plants draw water from the soil, transfer it to their leaves and it then evaporates
What is evapotranspiration?
The combination or evaporation and transpiration
What can ecosystem services be classified as?
Ecosystem services can be classified as cultural, provisioning, regulating and supporting, each of which can be applied to water.
What does the rate at which water infiltrates the ground depend on?
The rate at which water infiltrates into the ground depends on the permeability of the rocks and the state of the ground surface. Below the ground surface is an unsaturated zone which has air in the pore spaces, and a saturated zone which has all the pores filled with water.
What is an unconfined aquifer?
Unconfined aquifers outcrop at the ground surface; water normally has to be pumped to the surface from the water table in these aquifers.
What is water below the water table known as?
Water below the water table is called groundwater. The
Does the water table follow the topography?
The water table follows the topography of the ground surface but with gentler gradients.
What does darcys law relate?
Groundwater will flow in response to differences in elevation and pressure. Darcy’s law relates the rate of the groundwater movement (Q) to the hydraulic conductivity (K), the cross-sectional area (A) and the hydraulic gradient or slope of the water table (h/l):
What does hydraulic conductivity depend on?
The hydraulic conductivity depends on the permeability of the rock and the properties of the water. Water generally flows in the direction of the hydraulic gradient and the slope of the water table.
Pumping water from wells or boreholes lowers the water level (or potentiometric surface) in the surrounding area. Water flows into the borehole, and this creates a cone of depression around it. The difference in height between the water table before pumping and the water level in the well during pumping is called the drawdown.
What is the drawdown?
What does the depth of saline water under a land at the coast depend on?
There is usually saline groundwater under the land at a coast, with a wedge of denser saline groundwater under the fresh groundwater. The depth to the saline groundwater depends on the height of the water table above sea level and the densities of the fresh and saline water.
What is porosity a measure of?
Porosity is a measure of how much water a rock can store
What is permeability a measure of?
The permeability of a rock is a measure of the properties of the rock which determine how easily water can flow through it.
What type of rocks are porosity and permeability generally greater in?
The porosity and permeability are generally greater in unconsolidated sedimentary rocks, particularly sands and gravels, than in consolidated sedimentary, igneous or metamorphic rocks.
What processes can increase porosity and permeability and what is this known as?
Both porosity and permeability can be increased by processes that occur after the formation of the rock, such as solution or fracturing. These are called secondary porosity and secondary permeability.
What is an aquifer?
An aquifer is a body of rock that can store water, and through which water can flow.
What qualities must a rock have to be a good aquifer?
For a rock to be an aquifer it must be sufficiently porous and it must be permeable.
What type of rocks do not make good aquifers?
Igneous and metamorphic rocks seldom make good aquifers unless they have both secondary porosity and secondary permeability.
What is specific yield?
The proportion of water that can be recovered from a saturated aquifer is known as the specific yield
What will flood alleviation around a river depend on?
Flood alleviation will depend on individual river characteristics.
What is an unconfined aquifer?
Unconfined aquifers outcrop at the ground surface; water normally has to be pumped to the surface from the water table in these aquifers.
What is a confined aquifer?
Confined aquifers are separated from the ground surface by an impermeable layer.
What is artesian water?
Water in confined aquifers is called artesian water, and wells that penetrate confined aquifers are called artesian wells.
What is the potentiometric surface?
The potentiometric surface is an imaginary surface joining the heights to which water will rise. For an unconfined aquifer, the potentiometric surface is the water table. If the potentiometric surface lies above ground level then water will naturally flow from a well.
What is the safe yield of an aquifer?
What would happen if you exceed the safe yield?
The safe yield of an aquifer is the maximum rate of extraction of water that does not produce a long-term decline in the average water table level or have any other adverse effect, such as a significant reduction in the flow to springs and rivers. Exceeding the safe yield (i.e. ‘mining’ groundwater) would necessitate pumping from progressively greater depths to obtain water, and might lead to a reduced flow to springs and rivers, and a deterioration in water quality.
What does the effectiveness of an aquifer as a water supply depend on?
The effectiveness of an aquifer as a water supply depends on the hydraulic conductivity, K and also on the thickness of the aquifer.
What is the transmissivity of an aquifer?
• The effectiveness of an aquifer as a water supply depends on the hydraulic conductivity, K and also on the thickness of the aquifer. The product K × b, where b is the aquifer thickness, is called the transmissivity of the aquifer.
How can aquifers be characterised?
Aquifers can be characterised in terms of their geological, hydrological and hydraulic properties. Measurements of these properties can be conducted in the field and in the laboratory.
How can you age groundwater?
Groundwaters move very slowly, particularly where they are confined. The age of a groundwater sample can be determined from levels of the radioactive isotopes, and also other tracers (such as CFCs) present in groundwaters.
What are the 4 main routes for precipitation to travel through a catchment?
The four main routes for precipitation to travel through a catchment are: channel precipitation, Qp; overland flow, Qo; groundwater flow, Qg; and throughflow, Qt.
What factors determine the relative importance of precipitation through a catchment?
• The factors determining the relative importance of the routes include: the nature of the ground surface, vegetation, and underlying soil and rock; topography; the duration of a rainstorm; and the existing water content of the ground.
What is a catchment area?
The area in which rainfall flows in to a river, lake or reservoir
What are hydrographs useful for?
• Hydrographs are useful for understanding river discharge patterns and predicting peak river flows. They can be used to link rainstorm and river flow rate with time and to estimate flood frequencies from discharge data.
What does the shape of a short period and long period hydrograph depend on?
• The shape of a short-period hydrograph (the record for a few days) depends on the size, shape, geology, vegetation and land use of the river catchment. The shape of a long-period hydrograph (e.g. for a year) depends primarily on the type of climate in the river catchment.
What is river flooding the result of?
River flooding is the result of a complex series of factors including precipitation, infiltration rates and routes of water flow
What will flood alleviation around a river depend on?
Flood alleviation will depend on individual river characteristics.
Where does the journey of a river begin?
The journey of a river begins at the source, which is often a spring or seepage, which occur at points where groundwater reaches the surface
Which part of a river has the most speed?
•The speed of water in a river channel is not uniform over a cross-section, being slower where the water is in contact with the riverbed and faster nearer the centre of the channel
What affects the speed of the river?
The nature of the riverbed also affects the water speed, as does the gradient.
What indicates the efficiency of the river flow?
The hydraulic radius of a river channel indicates the efficiency of the river flow.
Explain what a river is like with a low hydraulic radius?
Rivers with a low hydraulic radius are less efficient and have greater friction with the riverbed and banks
How can river speed be estimated?
• River speed can be estimated using a float, a flow rate meter, a V-notch weir, the Manning equation or dilution gauging.
What are the 2 major factors controlling the characteristics of estuaries?
Two major factors controlling the characteristics of an estuary are water flows (tides and currents) and depositional processes.
Where are the deep passages to the northern sea?
The deep passages to the northern seas are only in the Atlantic Ocean and they are relatively shallow.
What is deposition of fine estuarine sediments assisted by?
Deposition of fine estuarine sediments is assisted by flocculation and slack water at high tide.
What can colours or changes in smell of sediment detect?
• Changes in the colour and/or smell of a sediment can be used to detect the presence or absence of oxygen.
What can reservoirs be used for?
• Reservoirs increase the amount of water stored on the land surface. They can be used for water supply, river regulation, hydroelectricity generation or flood prevention.
What are the negative impacts of human built dams?
Reservoir projects involving large dams are increasingly subject to scrutiny, particularly on the grounds of sustainable development. The negative impacts of constructing a reservoir include the loss of a large area of land, human resettlement, ecological changes, dam failure, sediment filling, sediment loss to agriculture, soil salinisation and induced earthquakes.
What is pollution of water?
Pollution is the deterioration of water quality caused by human agencies that makes the water less suitable for use than it was originally. Water does not have to be completely pure to be considered unpolluted.
Why is rainwater slightly acidic?
Rainwater contains a greater relative proportion of dissolved gases, particularly carbon dioxide, than seawater, and this makes it slightly acidic.
What different sources can pollution come from?
domestic sewage, farms, industry, mining, quarrying and cooling.
Name some different types of pollutants?
There are many types of pollutants, including natural organic materials, living organisms, plant nutrients, organic and inorganic chemicals, sediments and heat.
What other parameters might be measured when measuring water quality?
In monitoring water quality several different chemical parameters might be measured (such as pH, water hardness, oxygen demand, nitrogen compounds, metals and pesticides).
How are most pathogens introduced in to the water?
Most pathogens are introduced into water as a result of animal or human faecal contamination.
What are routine microbial indicators of water quality?
Routine microbial indicators of water quality are coliforms, E. coli and enterococci.
What happens to sewage? Where does it end up?
Sewage treatment aims to reduce the amount of organic and suspended solid material present, remove toxic materials and eliminate pathogenic bacteria, mainly by settlement of biological processes. The effluent is discharged into rivers, lakes or the sea, and the remaining sludge may be dumped at sea (but not in the EU), disposed of on farmland, dumped in landfills or incinerated.
Explain the hydrology of permafrost affected regions?
The hydrology of permafrost-affected regions is typically highly seasonal with runoff restricted to a few weeks in spring/summer, and is influenced by unfrozen groundwaters circulating in taliks, river freezing/thawing and consequent flooding, and by the formation of icings, which provide an important redistribution of water between winter and summer.
How is heat moved around the planet?
Heat is moved around the planet by the oceans and can affect regional climate
What are typical features of the oceanic floor?
Typical features of the oceanic sea floor include the continental shelf, abyssal plains and mid-ocean ridges.
Where are the deep passages to the northern sea?
The deep passages to the northern seas are only in the Atlantic Ocean and they are relatively shallow.
What makes the salt ions in seawater constant?
• The constancy of composition means that the ratio of many different dissolved salt ions in seawater is constant.
What heats the surface of seawater?
• Seawater is heated at the surface by solar radiation and the salinity of seawater is controlled by the balance between evaporation and precipitation, E–P.
What is the effect of wind stress on the surface of the ocean passed through?
• The effect of the wind stress on the surface of the ocean is passed down through the water column through eddy viscosity and energy is transferred into the water column.
What is the net result of the ekman spiral in the north and south hemisphere?
• The net result of the Ekman spiral in the Northern Hemisphere is to cause a slow transport of moving water to the right of the wind. In the Southern Hemisphere it causes a slow transport of moving water to the left.
What drives the ocean conveyor belt? What does it also do?
• The processes that drive a circulation pattern throughout the Atlantic Ocean also operate in the other oceans of the world. The differing densities of water have set up a global circulation pattern which is drawn
schematically as an ‘oceanic conveyor belt’ that redistributes large amounts of heat around the Earth.
What is the crysophere?
• The majority of fresh water on the surface of the Earth is in the form of snow and ice, and is known as the cryosphere
What is the state of health of an ice massed expressed through?
• The state of ‘health’ of an ice mass is expressed through its mass balance: the sum of mass gain (accumulation) and mass loss (ablation). When an ice mass is in a state of equilibrium with the climate, the annual net mass balance is zero; this rarely occurs in practice.
Explain the run off of snow and ice?
Snow and ice assume great importance in the hydrology of catchments. Runoff is low or even absent in winter, increases greatly with the onset of spring/summer, then dwindles again as the snow cover diminishes. This is the opposite of typical catchments.
How can glaciers have a dramatic impact on the landscape?
• Glaciers erode, transport and deposit rock debris and can have a dramatic impact on the landscape.
What percentage of earth is affected by periglacial conditions?
• As much as 25% of the Earth’s surface is affected by periglacial conditions, characterised by intense frost weathering and permafrost.
What is permafrost?
Generally regarded as permanently frozen ground, but more correctly perennially cryotic ground.
Name some perglacial landscape processes?
• Periglacial environments exhibit many distinctive landscape processes, including frost weathering, frost heaving, frost creep, frost cracking and gelifluction.
Explain the hydrology of permafrost affected regions?
The hydrology of permafrost-affected regions is typically highly seasonal with runoff restricted to a few weeks in spring/summer, and is influenced by unfrozen groundwaters circulating in taliks, river freezing/thawing and consequent flooding, and by the formation of icings, which provide an important redistribution of water between winter and summer.
What are hazards of the cryosphere?
Hazards include glacier advances and unstable glaciers, ice avalanches, glacier floods, glacier–volcano interactions and snow avalanches. Some of these have caused great loss of life in mountain regions around the world.
What is the oceanic conveyor belt?
Global oceanic circulation through a series of strong currents, driven by deep water formation in the polar seas and heating of water in the tropical seas; an effect of temperature and salinity differences. Also called thermohaline circulation.
What are the layers of thin gas that surround the earth called?
• The Earth’s atmosphere is a thin layer of gas surrounding the planet. It has several distinct layers, including the troposphere, stratosphere and mesosphere.
Which layer of the atmosphere does most of the mass lye within?
Most of the mass of the atmosphere lies within the troposphere, within 8 - 15 km of the Earth’s surface. The troposphere is deeper at the Equator than at the poles.
Explain what happens to the temperature in the diffferent layers of the atmosphere?
The temperature falls with height within the troposphere, but increases within the stratosphere, then falls again in the mesosphere.
What gases is the atmosphere mainly made up of and to what ratio?
The atmosphere is made up of a mixture of gases but is mainly nitrogen and oxygen in a ratio of roughly
4 : 1.
What does the amount of solar radation that a location on the earth depend on?
The amount of solar radiation that a location on Earth receives depends strongly on its latitude and the season of the year.
Which part of earth receives the most radiation and which part radiates the most?
The Earth receives an excess of solar radiation at the Equator but radiates more than it receives at the poles.
What does the motion of the atmosphere play a large part in?
• The motion of the atmosphere plays a large part in moving heat from the Equator to the poles and gives rise to the weather.
What is the stability of the atmosphere to vertical motions determined by?
• The stability of the atmosphere to vertical motions is determined by the rate of decrease of temperature with height.
What does the rotation of the earth play a crucial role in in terms of weather?
• The rotation of the Earth plays a crucial role in determining the large-scale circulation in the atmosphere of the Earth, constraining the circulation cells and resulting in mid-latitude weather systems. The rotation direction is opposite in each hemisphere.
What is pressure in the atmosphere related to?
Pressure is a fundamental variable which describes the atmosphere and is related to the total mass of air above any point.
What happens to pressure with increasing height?
• Pressure falls exponentially with increasing height above the surface.
What are horizontal pressure gradients closely related to?
• Horizontal pressure gradients are closely related to winds;
How can precipitation occur?
• Precipitation can occur as rain, snow or hail, but largely forms initially in clouds as ice crystals.
Why do winds tend to follow pressure contours?
• Winds tend to follow pressure contours as a result of the Coriolis Effect largely balancing the pressure gradient force.
What is the coriolis effect?
The influence of the Earth’s rotation on the motion of air across its surface which produces an apparent deflection of air to the right of the direction of motion in the Northern Hemisphere, and to the left of the direction of motion in the Southern Hemisphere.
What is the coriolis force?
An apparent force invented to explain the deflection of bodies moving over the surface of the Earth without being frictionally bound to it. It acts 90° to the right of the direction of motion in the Northern Hemisphere, and 90° to the left in the Southern Hemisphere.
what is the Ekman Spiral?
The vertical spiral pattern of water velocities that develops in the upper ocean as a result of the Coriolis force acting on moving water. The pattern develops to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere.
Which direction do winds circle in the northern and southern hemisphere?
Winds circle low pressure systems anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. The rotation is opposite for high pressure systems.
What is temperature related to?
• Temperature is related to the mean speed of molecules in a gas and has a major impact on both the environment and human life.
What does the ideal gas equation of state link?
• The ideal gas equation of state links the pressure, temperature and density of air. If any two of these variables are known, the third can be determined.
what is specific humidity?
The specific humidity is a measure of the total amount of water in the air.
What is relative humidity?
The relative humidity indicates how close the air is to the condensation temperature and so how dry the air will feel.
What can a psychrometric chart be used to convert?
A psychrometric chart can be used to convert between drybulb temperature, wetbulb temperature, partial pressure of water vapour and relative humidity.
How does water condensation play a large role in determining the stability of the troposphere?
• Water condensation plays a large role in determining the stability of the troposphere. Conditionally unstable air is stable to a dry ascent but unstable to the ascent of a parcel of air which is saturated and warmed by the condensation of water.
When do clouds, mists and fogs form?
Clouds, mists and fogs form when the air reaches its dewpoint temperature.
What is the dewpoint temperature?
The temperature to which the drybulb temperature of an air sample must fall to produce saturation, at constant barometric pressure and absolute humidity.
What do the ten genera of clouds indicate?
• The ten genera of clouds indicate their formation mechanism and the type of precipitation, if any, that they are likely to form.
What are dews and frost a result of?
Dews and frosts result from the condensation of water or ice directly on the surface.
How can precipitation occur?
• Precipitation can occur as rain, snow or hail, but largely forms initially in clouds as ice crystals.
What type of radiation is the most important in atmospheric energy?
The most important for atmospheric energy transfers are ultraviolet, visible and infrared radiation.
What type of waves are solar radiation and which part of the electromagnetic spectrum are they on?
Solar radiation is mainly in the ultraviolet and visible parts of the electromagnetic spectrum.
What part of the electromagnetic spectrum is terrestrial radiation mainly on?
Terrestrial radiation is mainly in the infrared part of the spectrum.
What happens to electromagnetic radiation by gases and particles as it passes through the atmosphere?
Electromagnetic radiation is scattered and absorbed by both gases and particles in the atmosphere.
What is the bulk composition of the atmosphere and what percentage are trace gases? What is the most abundent trace gas?
The bulk composition of the atmosphere is a mixture of nitrogen (N2) and oxygen (O2) gases. Trace gases make up less than 0.1% by volume, the most abundant being methane (CH4).
What is meteorology and what does it measure?
• Meteorology is an observational science and a wide variety of instruments are used to measure atmospheric variables, including pressure, temperature, wind, humidity, clouds, precipitation, sunshine and constituent gases.
What is weather a result of on a global scale?
The weather is a result of global-scale processes which move heat from the Equator to the poles.
What cells dominate in low latitudes?
At low latitudes, the circulation is dominated by longitudinally symmetrical Hadley cells.
What type of weather systems dominate in mid latitude?
At mid-latitudes, waves take over most of the heat transport, which manifests at the surface as low-pressure and high-pressure weather systems.
What cells dominate at high latitudes?
At high latitudes, polar cells form, associated with a polar high and subpolar low and a polar vortex in the upper winter troposphere.
Why does the northern and southern hemispheres have different weather patterns?
The Northern and Southern Hemispheres do not behave as mirror images of each other, largely as a result of the different distribution of land in each hemisphere.
What happens when colder and warmer air masses meet?
Where colder and warmer air masses meet at the polar front, instabilities can develop which then form mid-latitude depressions.
What are fronts in terms of weather?
The borders between air masses are called fronts. They behave differently according to whether warm air is advancing into cold air, or vice versa.
How can large mountain ranges change the weather?
The presence of large mountain ranges can enhance precipitation on the upwind side and form rain shadows on the downwind side.
Define the term climate?
Climate is a time average of weather statistics, formally taken over a period of 30 years.
What are hurricanes and typhoons examples of?
• Hurricanes and typhoons are examples of intense, low-pressure weather systems, more generally known as tropical cyclones.
What 5 conditions does a tropical cyclone require?
• The development of a tropical cyclone requires five conditions:
o a warm ocean surface (temperature above about 26 °C)
o a moist troposphere
o an atmosphere which is not too stable, to allow the development of deep cumulonimbus clouds
o light winds, which will not disrupt the developing structure
o initial development at least 5° latitude away from the Equator.
What hemisphere are tropical cyclones more common in?
• Tropical cyclones are more common in the Northern Hemisphere than in the Southern Hemisphere. The existence of any storms in the South Atlantic Ocean strong enough to be classed as tropical cyclones is in dispute.
What type of surfaces causes tropical cyclones to grow and weaken?
Tropical cyclones tend to grow in strength over warm tropical sea surfaces and to weaken over land surfaces and when they move to colder seas.
How are humans mainly affected by topical cyclones?
The impact of tropical cyclones on human life can depend more on the associated flooding and landslides than on the direct effects of the wind.
What is the bulk composition of the atmosphere and what percentage are trace gases? What is the most abundent trace gas?
The bulk composition of the atmosphere is a mixture of nitrogen (N2) and oxygen (O2) gases. Trace gases make up less than 0.1% by volume, the most abundant being methane (CH4).
Hoe does the wavelength affect the energy associated with it?
The shorter the wavelength (λ) of electromagnetic radiation, the higher the energy of the associated photons.
What happens to incoming solar UV radiation when passing through the atmosphere? What is photolysis?
Different atmospheric constituents absorb different wavelengths in the incoming solar UV radiation, leading to photolysis, splitting molecules into highly reactive fragments (free atoms and radicals), and hence initiating chemical change.
What layer in the atmosphere is ozone most abundent?
• Ozone (O3) occurs in trace amounts throughout the atmosphere, but its concentration varies markedly with altitude. Concentrations peak in the ozone layer in the stratosphere
How is ozone in the atmosphere formed?
All ozone in the atmosphere is formed photochemically – from the photolysis of O2 (at λ < 240 nm) in the stratosphere.
Why does the temperature increase in the stratosphere?
• Absorption of solar UV radiation during the ozone cycle heats the stratosphere and is responsible for the temperature inversion at the tropopause (the boundary between the troposphere and stratosphere).
How is ozone formed in the stratosphere?
• All ozone in the atmosphere is formed photochemically – from the photolysis of O2 (at λ < 240 nm) in the stratosphere
How is ozone formed in the troposphere?
from the photolysis of NO2 (at λ < 400 nm) in the troposphere
How has background ozone in the troposphere formed?
• Background levels of tropospheric ozone have increased over the past century, alongside the growth in anthropogenic sources of the main precursor gases (CH4, CO and NOx). These sources include enhanced biogenic emissions (linked to food production, waste management and biomass burning) and emissions related to the extraction or distribution and the combustion of fossil fuels
What primary pollutants are emitted from a vehicle?
The classes of primary pollutants emitted from a vehicle with an internal combustion engine (in addition to H2O and CO2) are carbon monoxide (CO) and a wide range of unburnt hydrocarbons (HCs), accompanied by other partial oxidation products. In addition, nitric oxide (NO) is generated by the fixation of nitrogen from the air at the high temperatures involved in the combustion reaction. On leaving the exhaust system, NO can be oxidised to NO2, so that, overall, NOx is a pollutant.
What particulate matter is emitted from the internal combustion engine?
A further important emission arising from the internal combustion engine is particulate matter (PM). Typically, this is made up of carbonaceous material with volatile organic compounds (VOCs) either sorbed on the solid matter or present as hydrocarbon droplets. Sulfates and nitrates can also be present.
What causes acid rain?
one of the primary pollutants, including PM, are desirable additions to the atmosphere, causing significant health problems and contributing to environmental hazards such as acid rain.
What is the major factor in the build-up of NOx and hydrocarbons in the atmosphere?
Emissions from motor vehicles are a major factor in the build-up of NOx and hydrocarbons in the atmosphere, and hence the problem of photochemical smog.
What systems are in place to cut motor vehicle emissions?
Pollution abatement measures designed to drastically cut motor vehicle emissions involve various catalytic systems. • A three-way catalytic converter in petrol driven vehicles is fitted into the exhaust system.
How do catalyst converters achieve control of exhause emissions?
Control of exhaust emissions is achieved by promoting reactions that have the net effect of simultaneously oxidising CO and HCs (to CO2 and CO2 + H2O, respectively) and reducing NO (to harmless N2).
What main elements are the earths crust formed of?
• The rocks of the Earth’s crust are composed of minerals, principally formed from the elements oxygen and silicon
What is the rock cycle?
• The rock cycle, in which any rock may be converted into other rock types, is a cycle in which rocks are continually formed and destroyed.
How are igneous rocks formed?
Igneous rocks are formed by the cooling and crystallisation of magma. Examples are ocean-floor basalts, and andesite and granite of the continental crust.
How are sedimentary rocks formed?
• Weathering and erosion of pre-existing rocks, resulting from interaction with water and the atmosphere, lead to the formation of sediments. Subsequent compression and cementation (the lithification process) give rise to sedimentary (or fragmentary) rocks, which include sandstones and shales (or mudstones). Limestones are usually formed from fragments of ancient life forms. ?
What are metamorphic rocks?
Metamorphic rocks – gneiss, schist and slate – are former igneous or sedimentary rocks, transformed by heat and pressure. They frequently contain minerals which differ from those in the source rock, often distributed in layers.
What can igneous rocks in the earths crust be divided in to?
Igneous rocks in the Earth’s crust can be divided into coarse-grained (intrusive) and fine-grained (extrusive) groups.
What does grain size of a rock depend on?
Grain size depends on the rate of cooling.
What do MAfic rocks contain a high proportion of?
• Mafic rocks contain a high proportion of the mafic (ferromagnesian) minerals olivine and pyroxene, so they have high levels of iron, magnesium and calcium. Felsic
What do felsic rock contain a high proportion of?
Felsic rocks have a high proportion of the felsic minerals feldspars and quartz (silica), so they have more sodium, potassium and silicon.
what do intermediate rocks mainly contain?
Intermediate rocks have mainly feldspar and amphibole.
As magma cools which minerals crystallise first?
As magma cools, mafic minerals crystallise first, then pyroxene and amphibole, then feldspars and mica and, finally, quartz
What causes metamorphic rocks?
• Heat from cooling magma, or heat and pressure from deep burial or tectonic activity, bring about contact and regional metamorphism, respectively. More intense metamorphism results in larger crystals.
How are metamorphic rocks different from the original rock
• Metamorphic minerals have closer packed crystal structures than the original rock.
What are the three main clay minerals? and how are they structured?
• The three main clay minerals are kaolinite (aluminium-rich), illite (potassium-rich) and montmorillonite (iron/magnesium-rich). They have a layered structure of 1 : 1 or 2 : 1 sheets of silicate tetrahedra and aluminium (or magnesium) octahedra with metal ions between the layers.
What do limestone consist mainly of?
• Limestones consist mainly of calcium carbonate, generated by chemical precipitation (e.g. oolitic limestone) or from fossil fragments, and cemented by calcite.
What are the three main silicate sedimentary rocks?
• Silicate-based sedimentary rocks – conglomerates (breccias), sandstones and mudstones (shales) – are classified according to size, sorting and fragment shape.
What interacts to to result in physical and chemical weathering?
• The interaction between the atmosphere, water and rock-forming minerals results in physical and chemical weathering.
What are the different types of physical weathering?
• Physical weathering is a mechanical process, breaking rocks into smaller fragments through frost shattering, crystal formation, heating and cooling, root growth, and attrition during transport.
Why does chemical weathering occur?
• Chemical weathering occurs because minerals formed at depth are unstable at the Earth’s surface, in the presence of oxygen and aqueous acid (especially CO2 in water). Silicate rocks disintegrate, forming new minerals, an aqueous solution of metal ions and ‘silicic acid’ (sometimes called ‘soluble silica’), and residual resistant material.
What does calcium in limestone dissolve in to?
• Calcium carbonate in limestone dissolves to form calcium and hydrogen carbonate ions.
When a primary mineral weather to a clay mineral what does it become deficient in?
When a primary mineral weathers to a clay mineral, it becomes deficient in potassium, sodium, calcium, magnesium and silicon, which weather out more easily than aluminium or iron.
What are all clays enriched and depleted of?
All clays are enriched in aluminium compared with the original mineral, but depleted in silicon.
What are the highly weathered soils of the tropics dominated by?
• The highly weathered soils of the tropics are dominated by hydrated oxide clays, oxides and hydroxides of iron, aluminium or manganese, which are formed by hydrolysis and oxidation reactions.
What can the rocks beneath your feet be?
The rocks beneath your feet can be either the bedrock geology (the solid rocks – igneous, Hi sedimentary or metamorphic) or, where they occur, the superficial deposits (recent unconsolidated sediments) overlying the bedrock, or a combination of both.
What three sources does the energy for transporting material into and out of the landform system come from?
The energy for transporting material into and out of the landform system comes from three sources: the Earth’s internal heat, solar radiation and gravity.
What 4 steps in the process of erosion divided in to?
• The process of erosion is divided into four steps: detachment, entrainment, transport and deposition
What are fluvial processes driven by?
• Fluvial processes are driven by the potential energy of water, evaporated from the sea and precipitated at higher elevations.
What does fluvial mean?
of or found in a river.
What can material transported by streams be divided in to?
• Material transported by streams can be divided into three fractions: dissolved load, suspended load and bedload.
What can be calculated to determine the extent at which a stream is straight, meandering or braided
• The extent to which a stream is straight, meandering or braided is determined by calculating the sinuosity and braiding index.
What is the height of a wave determined by?
• The height of a wave is determined by the fetch and the wind speed.
How can a wave contribute to a beach?
• Depending on the height and wavelength, a wave may be constructive and build up a beach, or destructive and remove material from a beach.
What is longshore drift?
• Wave action erodes material from the coastline and transports it along the beach by longshore drift.
How can glaciers physically shape landscape?
• Glaciers and ice sheets can physically shape landscapes by the erosion, transportation and deposition of material through the landscape.
What physical actions lift material into ice?
• The physical actions of scooping, plucking and scouring lift material into the ice.
What erosive features indicate that glacial action has removed material locally?
• Erosive features, such as cirques, arêtes, horns and glacial trough valleys, indicate that glacial action has removed material locally.
What depositional features indicate that material has accumulated locally as a result of glacial action?
• Depositional features, such as moraines, eskers and erratics, indicate that material has accumulated locally as a result of glacial action.
How does wind erode material?
• Wind erodes material by deflation and abrasion.
How does wind transport eroded material?
• Wind transports eroded material by suspension, saltation and traction (surface creep).
What are dunes
• Dunes are asymmetrical with a gentle windward slope and a steep leeward slope. The movement of grains up and over the dune causes the slope to migrate downwind.
dunes occur in a number of forms depending on….?
• Dunes occur in a number of forms, depending on wind strength, wind direction, sediment supply and vegetation cover.
What are soils
• Soils are naturally occurring, unconsolidated materials consisting of mineral and organic components that are potentially capable of supporting plant growth.
What are soils composed of?
• Soils are composed of inorganic matter, organic matter, water and air.
What are important basic soil qualities?
• Soil structure (the organisation of the soil) and soil texture (the proportions of different particle size fractions) are important basic soil properties.
What does carrying out a risk assessment involve?
• Carrying out a risk assessment involves:
o identifying the hazards
o identifying the possible harm and seriousness of that harm
o assessing the likelihood of the hazard occurring.
The risk is the product of the likelihood that a hazard will cause harm and the seriousness of the harm.
